[Historical and current pathophysiological concepts of stress (Tako-Tsubo) cardiomyopathy]

[Patient care in the acute phase of stress induced cardiomyopathy (Tako-Tsubo cardiomyopathy)--and thereafter?]

The prognosis of patients presenting with Tako-Tsubo cardiomyopathy (TTC) is generally considered to be favorable. However, in the acute phase of the disorder complications are not infrequent and, therefore, continuous monitoring and consistent therapy in an intensive care unit is essential. Typical complications in patients with TTC are cardiogenic shock, obstruction of the left ventricular outflow tract (LVOT), occasionally accompanied by acute mitral regurgitation, arrhythmias, predominantly torsade de pointes tachycardias due to QT prolongation, left ventricular (LV) thrombus formation with or without consecutive thromboembolic events, and LV rupture. After confirmation of TTC by coronary angiography, repeat echocardiography should be performed. A standardized therapy for patients with TTC has so far not been established. Recommendations for the acute phase include the administration of anxiolytic agents for patients who present with preceding emotional stress, consistent therapy of physical stressors (such as pain or asthma) and avoidance of catecholamine therapy. Shock due to LVOT obstruction is treated by administration of volume and β-blockers. With respect to the occurrence of torsade de pointes tachycardias, drugs which might cause QT prolongation should not be given. The notable incidence of LV thrombus formation justifies therapeutic anticoagulation. Systematic studies and treatment recommendations for the prophylaxis of recurrent TTC do not exist. The recently reported association between TTC and malignant disorders should prompt tumor screening and subsequent preventive medical checkups in patients affected by TTC.

Novel aspects and new roles for the serine protease plasmin

The serine protease plasmin is distributed throughout the human body in the form of the zymogen plasminogen. The plasminogen activation system is mostly recognized for its fibrinolytic activity but is also upregulated in chronic inflammatory diseases, including atherosclerosis and arthritis. Plasmin can bind to a variety of cells, including monocytes, through low-affinity binding sites and triggers aggregation of neutrophils, platelet degranulation and arachidonate release from endothelial cells. In monocytes, plasmin elicits full-scale proinflammatory activation, including lipid mediator release, chemotaxis and cytokine expression, as well as induction of other proinflammatory genes. The effects of plasmin are specific, require the active catalytic center and can be antagonized by lysine analogues, implying binding of the plasmin molecule to the cell membrane through its lysine binding sites. In view of the upregulation of the fibrinolytic genes in chronic inflammatory diseases, cell activation by plasmin is likely to play a major pathophysiological role, a view that is further supported by data from transgenic mice.

Targeting of the Akt/PKB kinase to the actin skeleton

Serine/threonine kinase Akt/PKB intracellular distribution undergoes rapid changes in response to agonists such as Platelet-derived growth factor (PDGF) or Insulin-like growth factor (IGF). The concept has recently emerged that Akt subcellular movements are facilitated by interaction with nonsubstrate ligands. Here we show that Akt is bound to the actin skeleton in in situ cytoskeletal matrix preparations from PDGF-treated Saos2 cells, suggesting an interaction between the two proteins. Indeed, by immunoprecipitation and subcellular fractioning, we demonstrate that endogenous Akt and actin physically interact. Using recombinant proteins in in vitro binding and overlay assays, we further demonstrate that Akt interacts with actin directly. Expression of Akt mutants strongly indicates that the N-terminal PH domain of Akt mediates this interaction. More important, we show that the partition between actin bound and unbound Akt is not constant, but is modulated by growth factor stimulation. In fact, PDGF treatment of serum-starved cells triggers an increase in the amount of Akt associated with the actin skeleton, concomitant with an increase in Akt phosphorylation. Conversely, expression of an Akt mutant in which both Ser473 and Thr308 have been mutated to alanine completely abrogates PDGF-induced binding. The small GTPases Rac1 and Cdc42 seem to facilitate actin binding, possibly increasing Akt phosphorylation.